The present invention pertains to the field of image data processing. More specifically, the invention relates to a system and method for locating irregular edges in image data that allows features having irregular edges to be detected.
Image data processing is used to inspect items during and after the manufacturing process. Such image data is typically gathered using a digital camera or other device that digitizes image data within the focal field of the device. The digitized image data is then analyzed, either manually or by software systems or other digital systems.
In cases where the image data is more complex, it is often necessary to manually review the image data before software systems can be used. For example, image data of dies that have been cut from a silicon wafer can be inspected by software systems. Nevertheless, areas of the die may have to be manually selected that cannot be analyzed by the software systems, such as areas that contain image data that will cause the software systems to register a false indication of a problem. In other circumstances, it is easier to select areas that are to be inspected, rather than areas that are to be excluded from inspection.
Therefore, although analysis of image data by software systems is useful, manual selection of image data may still be required. One area in which such manual selection can be required is the identification of probe marks on bond pads of a silicon wafer die. The irregular edges of a probe mark make probe marks difficult to detect, as opposed to straight edges between areas that differ in brightness. Thus, it is necessary to manually identify probe marks in order to determine whether the probe marks are closer to the edge or larger in area than may be allowed. Such manual detection is time consuming, and can also result in improper results. Nevertheless, known systems and methods for analyzing image data do not provide for any other way to identify such features having irregular edges.
In accordance with the present invention, a system and method for locating features in image data are provided that overcome known problems with locating features.
In particular, a system and method for locating features in image data are provided that allow irregularly shaped edges of features to be located.
In accordance with an exemplary embodiment of the present invention, a system for processing image data, such as an image of a die cut from a silicon wafer, is provided. The system includes an irregular edge detection system, which can locate edge data of a feature of the image data, such as the edge of a probe mark in a bond pad. A feature area calculation system is connected to the irregular edge detection system, such as by accessing data stored by the irregular edge detection system. The feature area calculation system can receive the edge data of the feature and determine the area of the feature, such as by summing normalized pixel area values. The irregular edge detection system uses interpolation to locate edges that occur between the centerpoints of adjacent pixels.
The present invention provides many important technical advantages. One important technical advantage of the present invention is a system and method for locating irregular edges in image data that can discriminate between random variations and anomalies and actual features of interest, such as probe marks. The present invention also provides for sub-pixel location of feature edges, and sub-pixel approximation of the area of features, both of which provide more accurate estimates of feature location and size than known systems and methods for locating and sizing features.